Ring position

[vortex99ozman]

Has anyone got and idea of the position of the rings for an 150 bigfoot widowmaker. The rings are marke "D" and the other one has "DY" on it.

 

[Cactus Jack]

OK mate , since we all don't seem to have a clue about the bike in question ... I decided to use a little logic and check out a brand new Lifan "138" kit which came supplied with the rings already fitted to the piston ... and "BINGO" ... The top ring looks like black cast iron and has a "D" marked on it ... The ring is installed in the top ring groove with with the "D" facing down ... The ring appears to have a very slight chamfer on the outside bottom edge with the "D" on it and the edge that goes to the top is sharp ... That makes sense because you want the sharp edge at the top to help seal in the combustion pressure and the chamfered edge at the bottom to allow a very slight fraction of oil to get past to lubricate the ring face and cut friction ...

The second ring appears to be hard chromed and has "DY" marked on the side that faces to the top of the piston ... it has chamfered edges on both sides ...

You install the piston into the bore with each compression ring end gap facing 180 degrees away from each other ... Start the gap in the top ring 180 degrees away from the bore thrust face which is the bottom of the cylinder in a horizontal engine and the front of the cylinder in a vertical engine ... The chinese have the oil ring installed on the "138" piston with the gaps in the ends of each scraper about 15 mm apart ... obviously to make it easier to get the ring set into the bore ... There's no point in having them 180 degrees apart since there are holes drilled into the middle of the oil ring groove ... so only the position of the gap in the top oil scraper would matter ...

Position the gap in the top scraper on the opposite side of the bore to the gap in the lowest compression ring ... Some engine builders do it slightly differently ... Apparently it's important to not have any gaps in line with the piston pin ... Rings rotate in the grooves so they're gunna end up in line with the pin at some point in time ...

Ring end gap positioning and staggering is done to give less chance for oil or combustion pressure to escape past 'em ... Think of it as creating a "Maze" to force any pressure or oil that leaks thru the ring end gaps to have to travel thru to reach the other side ... Hardly anything can pass thru the distance in the time it has to do it so a higher degree of combustion seal is achieved , giving the best compression and power ... Well that's the theory anyway ...

I've just found a better link which explains the do's and don'ts of piston ring installation and it has a diagram showing ring gap placement and staggering ... It's more important to use a proper ring expander to avoid stretching or twisting the rings ...

AutoZone.com | Repair Info | Piston Ring Set - How To Instructions

Here's a chinese link on ring installation ... I wish I found it before typing out this post ... LOL ...

Jiangsu Yizheng Wellong Piston Ring Co., Ltd.

 

[vortex99ozman]

Cheers for the help mate, good info.